Thermoplastic resins are thermally deformable, and this property allows the resins to be formed not only into flat shapes such as sheet- and film-like shapes but also into certain shapes such as spherical, cylindrical, and box-like shapes and to be used as products in various forms. However, the thermoplastic resins are basically transparent, relatively soft, and susceptible to scratches. Therefore, their surface is subjected to printing and coating for the purpose of protection or improvement in their aesthetic appearances.
The thermoplastic resins include polar resins and nonpolar resins. Among the nonpolar resins, polyolefin-based resins such as polypropylene and polyethylene are inexpensive, have many good properties such as good moldability, chemical resistance, water resistance, electrical characteristics, and safety, and are therefore widely used in recent years.
However, unlike the polar resins such as acrylic-based resins and polyester-based resins, the polyolefin-based resins are nonpolar and crystalline and therefore have a problem in that inks, coatings, adhesives, etc. do not easily adhere to the resins.
One method proposed to improve the above problem relating to the adhesion is to add a polyolefin-based resin to the inks, coatings, adhesives, etc. The solubility of chlorinated polyolefin resins in solvents other than aromatic solvents is low. Therefore, these chlorinated polyolefin resins are generally used after dissolved in an aromatic solvent such as toluene.
However, recently, from the viewpoint of environmental problems, chlorinated polyolefin resin compositions that use a solvent containing no aromatic solvent such as toluene are required in coating sites and printing sites. In one proposal to address this requirement (see Patent Literature 1), the polarity of a chlorinated polyolefin resin is increased by subjecting the chlorinated polyolefin resin to oxidation treatment or by reacting the chlorinated polyolefin resin with an acrylic-based monomer to form a graft copolymer, whereby the solubility of the chlorinated polyolefin resin in non-aromatic solvents such as ester-based solvents and ketone-based solvents is improved.